Without limiting the scope of the invention, its background is described mainly in connection with fusion energy. The increase in energy consumption and the disadvantages of hydrocarbon fuels has led to a search for alternate sources of energy. One such source is fusion energy from a thermo-nuclear fusion reactor, which offers an almost limitless source of energy. However, there are many scientific and engineering challenges.
Generally, a fusion reactor includes a fusion fuel, often a mixture of deuterium and tritium, that is heated to very high temperatures and confined for some time in a plasma state. The plasma state is generated using electrical energy. The plasma state contains ions that have sufficient energy to fuse. To fuse, the ions must be held together long enough for fusion to occur, e.g., magnetic confinement. Generally, the products of the fusion reaction may include elements such as helium, a neutron and energy. The energy released in most nuclear reactions is much larger than that for chemical reactions, because the binding energy that holds a nucleus together is far greater than the energy that holds electrons to a nucleus. In most reactor designs, the energy from the reaction is eventually collected as thermal energy which is subsequently converted into electricity.
There have been many fusion devices including the tokamak (i.e., a Russian word for a torus-shaped magnetic chamber) stellarator, z-pinch, spherical pinch, magnetized target fusion, laser, ion or electron beam and spheromak; however, these devices have not yet succeeded. One difficulty with the plasma heating approach has been instability in the plasma during the heating phase that has prevented the magnetic fields from being able to contain the heated, ionized gas for sufficient time to even reach the breakeven point in energy production.
One such method and apparatus for generating and utilizing a compound plasma configuration is taught in U.S. Pat. No. 4,023,065 issued to Koloc, which teaches a plasma configuration that includes a central toroidal plasma with electrical currents surrounded by a generally ellipsoidal mantle of ionized particles or electrically conducting matter. The methods of forming this compound plasma configuration include the steps of forming a helical ionized path in a gaseous medium and simultaneously discharging a high potential through the ionized path to produce a helical or heliform current which collapses on itself to produce a toroidal current, or generating a toroidal plasmoid, supplying magnetic energy to the plasmoid, and applying fluid pressure external to the plasmoid.
Another approach is the pulsed nuclear fusion reactor taught in U.S. Pat. No. 4,182,650 issued to Fischer, which relates to a nuclear fusion power plant for producing useful electrical energy by nuclear combustion of deuterium and lithium to helium. A large concentric plate capacitor is discharged rapidly through a mass of molten LiD that is situated at its center. Before this discharge, a conducting path had been thermally preformed between the electrodes by an alternating current pulse and the high-temperature, high-pressure plasma is confined by the LiD liquid in a narrow channel. Neutrons are generated, partly by thermonuclear fusion, partly by suprathermal collisions which result from the well-known sausage instability. The escaping neutrons are absorbed by the surrounding liquid where they produce heat. The heat, radiation and mechanical shock are absorbed in the liquid which flows through a heat exchanger in order to energize the associated turbogenerator power plant.
Still another approach is a compound plasma configuration and method and apparatus for generating a compound plasma configuration taught in U.S. Patent Publication No. 20010046273 to Paul M. Koloc, which relates to a compound plasma configuration formed from a device having pins and an annular electrode surrounding the pins. A cylindrical conductor is electrically connected to, and coaxial with, the annular electrode, and a helical conductor coaxial with the cylindrical conductor. The helical conductor is composed of wires, each wire electrically connected to each pin. The annular electrode and the pins are disposed in the same direction away from the interior of the conducting cylinder.
The dense plasma focus (DPF) has been studied as a possible solution to the problem of instabilities. In this device, natural plasma instabilities are used to create confinement in a dense plasmoid, rather than being minimized as in other fusion devices. One such method and apparatus for a dense plasma focus radiation source for generating EUV radiation including a coaxially disposed anode and cathode is taught in U.S. Pat. No. 7,002,168 issued to Jacob, et al. The methods and apparatuses for enhancing the efficiency of EUV radiation production, for protecting, cooling and extending the life of the anode and cathode, for protecting and shielding collecting optics from debris and pressure disturbances in the discharge chamber, and for feeding Lithium into the discharge chamber.
Another plasma focus radiation source for generating radiation at a selected wavelength is taught in U.S. Pat. No. 6,172,324 issued to Birx, which teaches producing a high energy plasma sheathe that moves down an electrode column at high speed and is pinched at the end of the column to form a very high temperature spot. An ionizable gas introduced at the pinch can produce radiation at the desired wavelength. In order to prevent separation of the plasma sheathe from the pinch, and therefore to prolong the pinch and prevent potentially damaging restrike, a shield of a high temperature nonconducting material is positioned a selected distance from the center electrode and shaped to redirect the plasma sheathe to the center electrode, preventing separation thereof. An opening is provided in the shield to permit the desired radiation to pass substantially unimpeded.
However, the DPF has also not yet achieved breakeven conditions and has never simultaneously achieved a high efficiency of transfer of energy into the plasmoid, high ion energy and high density. In addition, the DPF suffers from a high degree of variation in output from shot to shot even with identical initial conditions.
In addition to its application as a fusion reactor, the DPF has other important potential applications as a source of x-rays, ion beams and neutrons. Such applications include x-ray lithography, x-ray and neutron inspection, and medical isotope production. However, its application in these areas has also been hampered by its high degree of variability.
Attempts to overcome this variability have not been entirely successful. A plasma focus apparatus is taught in U.S. Pat. Nos. 5,075,522 and 4,912,731 issued to Nardi, which teaches plasma focus apparatus with a field distortion element in the interelectrode gap at the breech end displaced from the sleeve of insulating material between the electrodes. As a result the neutron yield of the accelerator is at least 5 times the yield in the absence of the field distortion element, e.g., in the shape of a knife blade.
A further difficulty of most approaches to fusion is that they rely on deuterium-tritium fuel, which produces high-energy neutrons. The neutrons generate induced radioactivity in the reactor structure. As well, the neutron energy must be captured as heat and converted to electricity by a standard steam cycle, which is very expensive and prevents any substantial reduction in the cost of electricity.
Alternate, advanced fuels that produce only charged particles could overcome this problem. It has long been recognized that the pB11 reaction, which produces 3 He4 ions and 8.7 MeV of energy, has great advantages as a fusion fuel. It produces only charged particles and thus the energy of the reaction can be converted directly into electricity, avoiding the very costly step of converting heat energy into electricity via a turbine and mechanical generator. This can lead to radical reduction in the cost of electricity. In addition, the reaction avoids the production of neutrons, which can induce radioactivity. A secondary reaction, B11+He4→n+N14 does produce approximately 0.2% of total energy in the form of low energy neutrons, but they have too little energy to activate reactor materials. Attempts have been made to use the pB11 reaction in fusion reactor designs.
One such method and apparatus for controlled fusion in a field reversed configuration and direct energy conversion is taught in U.S. Pat. Nos. 7,002,148, 6,894,446 and 6,850,011 issued to Monkhorst, et al., which teaches plasma ions magnetically confined in the FRC while plasma electrons are electrostatically confined in a deep energy well, created by tuning an externally applied magnetic field. Ions and electrons may have adequate density and temperature so that upon collisions they are fused together by the nuclear force, thus forming fusion products that emerge in the form of an annular beam. Energy is removed from the fusion product ions as they spiral past electrodes of an inverse cyclotron converter.
Another method and apparatus for the formation of a field reversed configuration for magnetic and electrostatic confinement of plasma is taught in U.S. Pat. No. 6,891,911 issued to Rostoker, et al., which teaches a Field Reversed Configuration (FRC) magnetic topology in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.
However, these attempts have not been successful so far as there are substantial technical challenges to using pB11. To use pB11 fuel the ion energies must be in excess of 100 KeV, simultaneously with density-confinement time products of more than 3×1015 particle-sec/cc. The higher atomic change, Z, of B11 greatly increases the x-ray emission rate, which is proportional to Z2 making it difficult to achieve ignition, e.g., the point at which the thermonuclear power exceeds the x-ray emission.
Finally, conversion of energy to electricity from both the ion beams and x-rays must be performed with high efficiencies. For high-energy x-rays this problem has not yet been solved in a practical manner.
The foregoing problems have been recognized for many years and while numerous solutions have been proposed, none of them adequately address all of the problems in a single device.